1. Field of the Invention
The present invention relates to an optical information recording medium, such as DVD (Digital Versatile Disc), CD (Compact Disc), in which a large amount of information such as letters, sound and animation is recorded and/or recordable as digital signals, an optical information recording substrate used in the medium, and a process for the preparation thereof, and further a photo-curable transfer sheet and a laminate useful in the preparation of the substrate.
2. Description of the Related Art
As an optical information recording medium in which digital signals have been already recorded by forming pits on its surface, CD and CD-ROM are widely used. Recently, DVD that the animation can be also recorded by forming pits on its both (double) sides has been noted as the next generation recording medium instead of CD and increasingly used. Further, attention is directed to recordable discs such as CD-R, DVD-R and DVD-RW having groove(s) or grooves and pits thereon.
Conventional DVD having recording layers (surfaces) on its both sides includes a disc readable from double sides, as shown in FIG. 10, in which each of reflective layers 1a, 2a is formed on a surface of signal-pits of each of transparent resin substrates 1, 2 having the surface of signal-pits on its one side, and the two transparent resin substrates 1, 2 are bonded to each other through an adhesive layer 3 such that the reflective layers 1a, 2a are faced to each other; and a disc readable from single side, as shown in FIG. 11, in which a semitransparent reflective layers 1b is formed on a surface of signal-pits of a transparent resin substrate 1 while a reflective layers 2a is formed on a surface of signal-pits of another transparent resin substrate 2 and the two transparent resin substrates 1, 2 are bonded to each other through an adhesive layer 3 such that the semitransparent reflective layers 1b and the reflective layer 2a are faced to each other.
The DVD readable from double sides can be prepared, for example, by subjecting melted polycarbonate resin to injection molding by the use of a stamper having unevenness (concave and convex) corresponding to the reverse of unevenness of the signal-pit to be recorded on the substrate to prepare a transparent resin substrate having unevenness on its surface, forming a reflective layer on the uneven surface by spattering metal such as aluminum on it, and bonding two transparent resin substrates obtained in the above manner to each other through an adhesive such that the two reflective layers are faced to each other.